The present invention relates generally to harvesters for tomatoes and other vine crops as well as to harvesters for seed crops such as wheat, barley, oats, rice, corn, milo, soybeans, sorghum, black-eyed peas, dried beans, safflower, Sudan grass seed, alfalfa seed and others. More specifically, the present invention relates to oscillating drum shaker apparatus utilized in the aforementioned harvesters for separating the seed kernels, fruits or vegetables from the plants of such crops.
Most seed crops have the characteristic that the crop for each plant comprises a relatively large number of small, lightweight seeds, grains or kernels (hereinafter collectively "kernels") which are attached to relatively bulky plant growths, frequently referred to as straw. To harvest the kernels they must be separated from the plants and the two are then segregated, the kernels being collected for subsequent transportation to points of use while the plants may be left on the field, burned or bundled as fodder for other uses.
Seed crop harvesters, now most commonly used in the form of self-propelled or pull-type combines, incorporate threshers which generally have a rotating cylinder the periphery of which is fitted with axially-oriented beater wings, usually provided with peripheral teeth, and a cooperating concave. The concave is trough-shaped and is defined by a multiplicity of axially-oriented, parallel bars carried by circumferential supports which are constructed to form relatively large, typically square openings through which loose kernels and chaff gravitationally drop for collection beneath the concave. Threshing is effected by passing the seed crop through a typically adjustable, closely-controlled, narrow gap between the beater wings of the cylinder and the rasp bars of the concave. As the seed crop passes through this gap the beater wings and the rasp bars mechanically strip the kernels from the straw.
A known variation on this technique of separating seed kernels from straw proposes threshing seed crops by moving them at a leisurely pace along a conveyor and subjecting the crops to vibrations, i.e., to a large number of cyclical accelerations and decelerations. The vibrations separate the kernels from plant growth by taking advantage of inertial forces between them which pull the two apart without the need for physically contacting them and stripping one from the other.
For example, U.S. Pat. No. 4,915,671 to Johnson, the full disclosure of which is incorporated herein by reference, describes an apparatus and method for threshing seed crops wherein the crop is fed onto a trough-shaped screen with openings through which seed kernels can pass, the crop being moved circumferentially along the screen by a rotating hub having a multiplicity of tines projecting radially therefrom. Superimposed on the rotational movement of the hub is a cyclical vibrational movement of rotational accelerations and decelerations. This causes the free tine ends to momentarily reverse their direction of movement as they rotate in an overall forward direction, creating a shaking action which separates the kernels from the plant and permits the kernels to work their way in a downward direction through the mass of plant growth until they reach the screen where they pass through openings for subsequent collection. The vibrational threshing device was found to enhance the yield of kernels, reduce the percentage of cracked kernels, and consume less power than was required for conventional thresher combines of comparable capacity. Further, the overall size and weight of the thresher could be reduced resulting in cost reductions in manufacturing and use.
The vibrational movement of the hub described in the '671 patent is accomplished by a vibratory drive having two counterweights secured to and rotating with corresponding shafts, which are driven by pulleys and belts from a hydraulic motor. A second hydraulic motor drives the rotation of the hub. The rotation of the counterweights superimposes onto the constant rotation of the drum a vibratory or oscillating motion which cyclically accelerates and decelerates the angular velocity of the drum.
A device similar to that described in the '671 patent has been proposed for use in tomato harvesters. U.S. Pat. No. 4,232,506 to Studer, the full disclosure of which is incorporated herein by reference, describes a method and apparatus for mechanically removing tomatoes from their vines after the vines have been severed from the roots and lifted above ground. The severed and lifted vines are fed in between a rotary drum with radially outwardly projecting rods, and stationary arcuate guide rods around the drum. The vines are shaken by subjecting them to angular acceleration and deceleration while the vines are transported around an arcuate path. The tomatoes shaken from the vines are collected, and the stripped vines are dropped back on the ground. The superposition of acceleratory motion on the constant angular velocity rotation of the drum is achieved through the rotation of two counterweights coupled to pulleys and driven by a motor.
Similarly, U.S. Pat. No. 4,335,570 to Fitzmaurice describes a harvester for vine crops such as tomatoes having a shaker head capable of being rotationally oscillated about its axis and tines adapted to engage the vines of the crop to be harvested. A support conveyor moves the vines under the shaker head while the tines of the shaker head shake the fruit therefrom. The oscillation of the shaker head is achieved using a two-counterweight mechanism, the counterweights rotationally driven by a chain coupled to a drive shaft. The shaking action is imparted by tines directly to the tomato vines causing tomatoes to separate from the vines and fall to the collection conveyors below.
While oscillating shaker-type devices like the aforementioned are relatively effective for removing the seed or fruit from the plant, it has been found that such devices impose a significant amount of undesirable vibrations on the frame of the harvester. Such vibrations vary with the speed at which the harvester is driven, and the frequency and amplitude of oscillation, but can become particularly pronounced as the resonant frequency of the harvester structure is approached. The vibration problem is further complicated by the tires and suspension on which most harvesters are carried, which act as springs, and can cause the harvester to gyrate vertically and laterally with respect to the ground.
In addition, it is generally known that for certain types of crops, a shaker-type harvester will more effectively remove the seed, fruit or vegetable from the plant if the amplitude of oscillation of the drum is increased. Oscillation amplitude is a function of the angular momentum of the rotating counterweights employed in such systems. Angular momentum is in turn dependent upon the mass of the counter-weights and their position relative to their axis of rotation. However, the mass of the counterweights is constrained by several factors. First, increasing the mass of the counterweights worsens the vibration problem discussed above. Second, the size and position of the counterweights is limited by the structural configuration of the harvester. In some harvesters, radial and/or axial clearance limits prohibit enlarging the counterweights or repositioning counterweights so as to increase angular momentum. In addition, harvester height and width must be kept within certain limits for highway transport. Further, the width of the counterweights is preferably minimized, since the counterweight mechanism and motor typically extend laterally outward from the harvester, where fast-moving, heavy machinery poses a safety hazard for people working on or near the harvester. Moreover, the overall weight of the harvester is sought to be minimized, since the ground on which the harvesters work is frequently soft. Such weight considerations further limit the size of the counterweights.
Because of these limitations on counterweight size, mass and position (and therefore oscillation amplitude), shaker performance is improved in known shaker mechanisms by raising the speed of counterweight rotation, and therefore oscillation, by running the shaker motor at a higher rpm. However, running the shaker at a higher speed accelerates wear and tear on the harvester, requiring more frequent maintenance, increasing part failures, and shortening harvester life.
Along with decreasing vibration and increasing the amplitude of shaker oscillation, improvement has been sought in the radially extending tines on the shaker drum. In known shakers, the tines are oscillated by the drum in accelerating/decelerating motion relative to the surface beneath the drum on which the plants are carried. Some plants manage to pass through the shaker without being stripped of all seeds, fruit or vegetables.
For these reasons, an improved drum shaker is desired which would eliminate the vibrational problem associated with known shakers. It would be desirable if the drum shaker provided increased oscillation amplitude without worsening vibration problems. Further, the drum shaker should not require substantial additional space for the motor and counterweight mechanism than that required for existing drum shakers. It would be further desirable if the drum shaker permitted lower speeds of operation and reduced wear and tear on components of the harvester. The drum shaker should more effectively separate seeds, fruit or vegetables from the plants to improve yield. Further, the drum shaker should not impair the safety of those working on or near the harvester.